show the volatility of a stock based on Standard Deviation around a Simple Moving Average. The bands widen when volatility increases and narrow when volatility decreases.
Bollinger Bands have 3 lines. The middle line is just the Simple Moving Average.
The Upper is calculated as SMA + (Standard Deviation * Number of Deviations).
The Lower is calculated as SMA - (Standard Deviation * Number of Deviations).
The default Period for the SMA and SD is 20 and the default Number of Deviations is 2.
The default input to Bollinger Bands is Close Price but you could use a Custom Input of Typical Price or Weighted Close instead.
Bollinger Band %b
Bollinger Band Width %